Lance Armstrong’s admission of steroid use in an interview with Oprah Winfrey reminds us of another apology by a superathlete for drug use. It is not Mark McGwire in pro baseball or Marion Jones in Olympic track, both of whom famously admitted using drugs as performance enhancers.

It is Michael Phelps. After winning eight gold medals at the 2008 Beijing Games, he fessed up to smoking marijuana.

His admission – for what seemed like casual use of pot at the time – hardly drew the same public outrage as now befits the cheating by Mr. Armstrong in the Tour de France cycling races. But it should have.

Both athletes set a bad example for younger athletes, many of whom are tempted to use any drug if they believe that talent, hard work, and mental determination will not be sufficient to succeed in a sport.

Some athletes use steroids for strength or to bulk up while others turn to pot in hopes of reducing stress and fear before competition or to numb pain. With either drug, the moral offense lies in diminishing the very idea of sport as a contest of merit and fair play. By definition, sport is manipulation of one’s body. But that presumably should be done largely by mental means and training.

No wonder no pro baseball player was elected to the Hall of Fame this year. Who can say which player relied on steroids to break records after the practice become so prevalent in recent decades?

Big sports leagues ban drug use, including marijuana , for competition. Yet their testing regimes are often weak and unable to keep up with the latest chemical inventions, especially in anabolic steroids. They must improve their screening – if only to help prevent school-age athletes from imitating famous athletes.

Take college sports. Last year, The Associated Press conducted a major investigation of the records of more than 61,000 players and found unusually high and sudden gains in weight – more than 20 pounds – for at least 7 percent of them. “Students posted such extraordinary weight gains across the country, in every conference, in nearly every school,” AP concluded, pointing a finger at steroids as the probable cause.

With two states, Colorado and Washington, having now legalized marijuana, it will be even more difficult for sports organizations to crack down on drug use. Pity those athletes visiting the US Olympic Committee facilities in Colorado Springs. They won’t get arrested in the state for smoking pot, but they will get bumped from their sport, and rightly so.

For Mr. Phelps, it’s not clear if he thought pot helped his swimming. Yet he was suspended by USA Swimming for using it. He told a TV station later that he talked to other athletes “in my shoes” to get their perspective.

So as the outrage over Armstrong’s drug use gains steam, let’s not forget the use of marijuana by athletes, either for “recreation” or to alter their performance, or both. Kids don’t need that kind of lesson from sports stars.